B–N–B Embedded multiple-resonance polyaromatic enabling efficient narrowband electroluminescence

Boron/nitrogen (B/N)-doped multi-resonance thermally activated delayed fluorescence (TADF) molecules have emerged as benchmark narrowband emitters for organic light-emitting diodes (OLEDs). However, these emitters face persistent challenges in synthesis and optoelectronic performance, notably aggregation-induced spectral-broadening and inefficient reverse intersystem crossing (RISC). Here, we introduce a molecular design that incorporates a B–N–B covalent-bond into a multiple resonance (MR) framework, synergistically combining narrowband emission of para-positioned B/N with a helically distorted B–N–B configuration that enhances spin-orbit coupling and suppresses molecular aggregations. A lithium-free, stepwise nitrogen-directed borylation enables high-synthesis-yield ( > 80%) targeted emitters, affording deep-blue (452 nm) and greenish (495 nm) TADF emissions with full-width-at-half-maximum of merely 12–14 nm, near-unity photoluminescence quantum yields and accelerated RISC rates ( > 105 s−1). Corresponding OLEDs simultaneously achieve high maximum external quantum efficiencies of 37.9–38.3%, narrow electroluminescence bandwidths of 15–17 nm and decent operational stabilities. This work establishes B–N–B integrated MR-TADF systems as a versatile platform toward high-performance organic optoelectronics. Organic light-emitting materials with narrow emission bands still struggle with difficult synthesis and performance losses from aggregation and slow spin conversion. The authors design a boron–nitrogen–boron molecular framework that improves spin interactions, limits aggregation, and yields efficient, narrow emission.